Chassis Connection System and Apparatus

ABSTRACT

Connecting a plurality of chassis using a rigid connection. A first coupling element of a first chassis may be mated with a first rigid connection. The first coupling element may be positioned on an exterior housing of the first chassis and coupled to a first backplane of the first chassis. A second coupling element of a second chassis may be mated with the first rigid connection. The second coupling element may be positioned on an exterior housing of the second chassis and coupled to a second backplane of the second chassis. Connecting the first chassis and the second chassis may allow the first and second backplanes to communicate analog signals.

CONTINUATION DATA

This application is a continuation of U.S. patent application Ser. No.12/341,549 titled “Connecting a Plurality of Chassis Using a RigidConnection” filed Dec. 22, 2008, whose inventor is James A. Reimund,which is hereby incorporated by reference in its entirety as thoughfully and completely set forth herein.

FIELD OF THE INVENTION

The present invention relates to the field of computer systems, e.g.,switching systems, and more particularly to a system and method forconnecting a plurality of chassis using a rigid connection.

DESCRIPTION OF THE RELATED ART

In recent years, chassis for computer systems have become increasinglypopular. In particular, chassis are particularly useful for test andmeasurement and industrial applications. Typical chassis include aplurality of slots for inserting expansion cards, e.g., for interactingwith or controlling various instruments or devices. However, once all ofthese slots are used, another chassis may be necessary. To address thisproblem, some previous systems included the ability to couple differentchassis together using communication cables. However, such cablesrequire hand wiring (which can result in misconfiguration) and canbecome tangled. Additionally, cable solutions often introduce latencyand signal degradation issues. Thus, improvements in chassis connectionsare desired.

SUMMARY OF THE INVENTION

Various embodiments are presented of a system and method for connectinga plurality of chassis using a rigid connection.

The system may include a first chassis, a second chassis, and/or a thirdchassis, e.g., up to n chassis.

The first chassis may include a housing defining one or more slots. Thehousing may include an exterior. The first chassis may further include afirst backplane included in the housing. The first backplane may beconfigured to receive one or more cards in the one or more slots.

The first chassis may also include a first coupling element positionedor included on the exterior of the housing. The first coupling elementmay be electrically coupled to the first backplane. The first couplingelement may also be configured to mate with a first rigid connection inorder to convey communication through the first rigid connection betweenthe first backplane of the first chassis and a second backplane of asecond chassis (e.g., via a coupling element (“second coupling element”)of the second chassis). Similar to above, the second chassis may includea housing defining one or more slots and including an exterior. Thesecond chassis may also include a second backplane included in thehousing which may also be configured to receive one or more cards in oneor more slots. Thus, the first and second chassis may be physicallydistinct with respect to each other.

In some embodiments, the first rigid connector comprises a circuitboard, e.g., a printed circuit board. Thus, the first rigid connectormay be configured to mate with the first coupling element of the firstchassis and mate with the second coupling element of the second chassis.After connection, the rigid connection may be configured to conveycommunication between the first backplane of the first chassis and thesecond backplane of the second chassis. In one embodiment, the rigidconnection may be configured to convey bus signals between the firstbackplane and the second backplane. For example, the rigid connectionmay be configured to convey analog bus signals between the first andsecond backplane.

The first chassis may further include another coupling element (“thirdcoupling element”). Similar to above, the third coupling element may bepositioned or included on the exterior of the housing and may beelectrically coupled to the first backplane. The third coupling elementmay be configured to mate with a second rigid connection in order toconvey communication through the second rigid connection between thefirst backplane of the first chassis and a third backplane of the thirdchassis. The second rigid connection may mate or connect with a couplingelement of the third chassis (“fourth coupling element”). Similar toabove, the third chassis may include a housing defining one or moreslots and including an exterior. The third chassis may also include athird backplane included in the housing which may also be configured toreceive one or more cards in one or more slots. Thus, the first andthird chassis may be physically distinct with respect to each other.

The method for coupling a plurality of chassis may include mating thefirst coupling element of the first chassis with the first rigidconnection. The method may further include mating the second couplingelement of the second chassis with the first rigid connection. Asindicated above, connecting the first chassis and the second chassisallows the first and second chassis to communicate. Additionally, thefirst backplane and the second backplane may communicate (e.g., analogbus signals) over the first rigid connector.

The method may further include mating the third coupling element of thefirst chassis with a second rigid connection. Furthermore, the fourthcoupling element of the third chassis may be mated with the second rigidconnection. Connecting the first chassis and the third chassis may allowthe first and third chassis to communicate. Additionally, connecting thefirst chassis and the third chassis allows the first, second, and thirdchassis to communicate.

BRIEF DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention can be obtained when thefollowing detailed description of the preferred embodiment is consideredin conjunction with the following drawings, in which:

FIG. 1 illustrates a computer system coupled to a chassis according toan embodiment of the present invention;

FIGS. 2A, 2B, and 2C illustrate a system comprising two chassis coupledto each other according to an embodiment of the present invention;

FIG. 2D illustrates an alternate embodiment for coupling two chassis toeach other;

FIG. 3 illustrates a plurality of coupled chassis according to oneembodiment of the invention; and

FIG. 4 is a flowchart diagram illustrating one embodiment of a methodfor connecting a plurality of chassis using a rigid connection.

While the invention is susceptible to various modifications andalternative forms, specific embodiments thereof are shown by way ofexample in the drawings and are herein described in detail. It should beunderstood, however, that the drawings and detailed description theretoare not intended to limit the invention to the particular formdisclosed, but on the contrary, the intention is to cover allmodifications, equivalents and alternatives falling within the spiritand scope of the present invention as defined by the appended claims.

DETAILED DESCRIPTION OF THE INVENTION Terms

The following is a glossary of terms used in the present application:

Computer System—any of various types of computing or processing systems,including a personal computer system (PC), mainframe computer system,workstation, network appliance, Internet appliance, personal digitalassistant (PDA), television system, grid computing system, or otherdevice or combinations of devices. In general, the term “computersystem” can be broadly defined to encompass any device (or combinationof devices) having at least one processor that executes instructionsfrom a memory medium.

Measurement Device—includes instruments, data acquisition devices, smartsensors, and any of various types of devices that are operable toacquire and/or store data. A measurement device may also optionally befurther operable to analyze or process the acquired or stored data.Examples of a measurement device include an instrument, such as atraditional stand-alone “box” instrument, a computer-based instrument(instrument on a card) or external instrument, a data acquisition card,a device external to a computer that operates similarly to a dataacquisition card, a smart sensor, one or more DAQ or measurement cardsor modules in a chassis, an image acquisition device, such as an imageacquisition (or machine vision) card (also called a video capture board)or smart camera, a motion control device, a robot having machine vision,and other similar types of devices. Exemplary “stand-alone” instrumentsinclude oscilloscopes, multimeters, signal analyzers, arbitrary waveformgenerators, spectroscopes, and similar measurement, test, or automationinstruments.

A measurement device may be further operable to perform controlfunctions, e.g., in response to analysis of the acquired or stored data.For example, the measurement device may send a control signal to anexternal system, such as a motion control system or to a sensor, inresponse to particular data. A measurement device may also be operableto perform automation functions, i.e., may receive and analyze data, andissue automation control signals in response.

Memory Medium—Any of various types of memory devices or storage devices.The term “memory medium” is intended to include an installation medium,e.g., a CD-ROM, floppy disks 104, or tape device; a computer systemmemory or random access memory such as DRAM, DDR RAM, SRAM, EDO RAM,Rambus RAM, etc.; or a non-volatile memory such as a magnetic media,e.g., a hard drive, or optical storage. The memory medium may compriseother types of memory as well, or combinations thereof. In addition, thememory medium may be located in a first computer in which the programsare executed, and/or may be located in a second different computer whichconnects to the first computer over a network, such as the Internet. Inthe latter instance, the second computer may provide programinstructions to the first computer for execution. The term “memorymedium” may include two or more memory mediums which may reside indifferent locations, e.g., in different computers that are connectedover a network.

Programmable Hardware Element—includes various hardware devicescomprising multiple programmable function blocks connected via aprogrammable interconnect. Examples include FPGAs (Field ProgrammableGate Arrays), PLDs (Programmable Logic Devices), FPOAs (FieldProgrammable Object Arrays), and CPLDs (Complex PLDs). The programmablefunction blocks may range from fine grained (combinatorial logic or lookup tables) to coarse grained (arithmetic logic units or processorcores). A programmable hardware element may also be referred to as“reconfigurable logic”.

FIG. 1—Computer System Coupled to a Chassis

FIG. 1 illustrates a computer system 50 that is coupled to chassis 100.As shown in FIG. 1, the computer system 50 may include a display deviceoperable to display a program (e.g., a graphical user interface to theprogram) as the program is created and/or executed as well as variousinput devices. The graphical user interface may comprise any type ofgraphical user interface, e.g., depending on the computing platform.

The computer system 50 may include at least one memory medium on whichone or more computer programs or software components according to oneembodiment of the present invention may be stored. The memory medium mayalso store operating system software, as well as other software foroperation of the computer system.

As also shown, the chassis 100 may include a backplane 110. In someembodiments, the backplane 110 may include a configurable hardware unit,such as a field programmable gate array (FPGA), which may be usable forconfiguring the chassis 100 to perform one or more functions (e.g.,using a subset or all of a plurality of cards inserted into thechassis).

As indicated, the chassis 100 may also include one or more (e.g., aplurality of) slots which may be configured to receive a correspondingplurality of pluggable cards. In one embodiment, the chassis 100 mayinclude a fixed number of slots, e.g., 4 slots, 8 slots, etc. Forexample, the cards may be any of various types, e.g., cards forcontrolling or interacting with instruments or devices, I/O cards forreceiving and/or manipulating data, computer cards (e.g., including aprocessor and memory medium or configurable hardware unit) which may beconfigured to perform computational functions, and/or other types ofcards, as desired. One or more of the plurality of cards may include aconfigurable hardware element which may be configured to perform one ormore functions.

The backplane 110 may provide one or more busses for communicating with(and between) the plurality of cards. In one embodiment, the bus may bean analog bus, e.g., which may be able to communicate test signals,although other busses are envisioned. The computer system 50 may beusable to configure and/or control the chassis 100. For example, thecomputer system 50 may be used to configure one or more of the cardsinserted in the chassis 100. In further embodiments, as indicated above,the backplane 110 of the chassis 100 may include a configurable hardwareunit (e.g., an FPGA), and the computer system 50 may be usable toconfigure the configurable hardware unit (e.g., with a graphicalprogram, such as one created using LabVIEW® provided by NationalInstruments Corporation). Thus, the computer system 50 may be usable tocontrol or configure the chassis 100 to perform one or more functions(e.g., industrial or measurement functions).

Embodiments of the present invention may be involved with performingtest and/or measurement functions; controlling and/or modelinginstrumentation or industrial automation hardware; modeling andsimulation functions, e.g., modeling or simulating a device or productbeing developed or tested, etc.

FIGS. 2A-2D—Two Coupled Chassis Via a Rigid Connection

As shown in FIGS. 2A-2C, the chassis 100 may be configured to couple toa second chassis 120 via a rigid connection 150A.

More specifically, as shown in FIG. 2A, the chassis 100 may include afirst coupling element 102 and a second coupling element 104. Thechassis 100 may also include a communication or physical interface 106,e.g., for connecting to a larger housing (e.g., the housing shown inFIG. 3).

As shown, the chassis 100 may include a front 108. The front 108 mayprovide an outlet for interfaces of the plurality of cards inserted intothe chassis. For example, various ports for ones of the plurality ofcards may be presented on the front 108 for coupling to other devices orcomputer systems (e.g., the computer system 50 of FIG. 1).

Similarly, the chassis 120 may include a first coupling element 122 anda second coupling element 124 as well as a communication or physicalinterface 126. Also similar to the chassis 100, the chassis 120 mayinclude a front 128 and a backplane 130.

As also shown, a rigid connection 150A may be configured to mate withthe coupling elements of the chassis 100 and 120. As used herein, “mate”or “mating” refers to direct physical connection of coupling elementsbetween two objects. For example, the rigid connection 150A may beconfigured to mate with the coupling element 104 of the first chassisand the coupling element 122 of the second chassis to couple the twochassis. In one embodiment, the coupling elements 104 and 122 of thechassis 100 and 120 may be half-connectors which may form a connectorfor mating to the mating portion 152A of the rigid connection 150A(i.e., to form a full mated connection). However, it should be notedthat other “matings” are envisioned, e.g., ones which may include a malecoupling element and a female coupling element.

In general, the rigid connection may provide a short connection betweenthe two backplanes, thereby avoiding tangling problems, latency issues(due to length of the connection between the chassis), and signaldegradation issues presented by prior art cable connections. As usedhere “short” may refer to a distance between the chassis of 1″, 2″, 3″or similar (e.g., shorter) distances. Longer distances (e.g., 5″) mayalso be used in other embodiments. However, it should be noted that inthe embodiments shown in FIGS. 2A-2C, the distance may be the thicknessof a single printed circuit board. Note that the rigid connection doesnot refer to typical cables, such as those used in prior art systems forcoupling two chassis.

The rigid connection may be configured to convey communication (e.g.,bus signals, such as analog bus signals, or other types of communicationor data signals) between the chassis 100 and the chassis 120. In someembodiments, the rigid connection may provide a direct connection ofsignals between the chassis 100 and the chassis 120. However, in oneembodiment, the rigid connection may include circuitry or logic whichmay be configured (or configurable) to perform one or more functions,e.g., signal processing functions. Additionally, the rigid connectionmay be usable for accessing backplane signals or measuring variouscharacteristics of signals being passed between the chassis 100 and thechassis 120, e.g. with digital multimeter (DMM).

In some embodiments, the rigid connection may be a circuit board, e.g.,a printed circuit board (PCB). For example, the rigid connection may bea printed circuit board with edge traces or pins used for mating withthe coupling elements of the chassis. More specifically, as shown, therigid connection may include mating portions 152A and 154A (shown asincluding edge traces). In this particular embodiment, mating portion152A may mate with coupling element 104 of the chassis 100 and couplingelement 122 of the chassis 120. In the embodiment shown, mating portion154A may not be used, e.g. may be short-circuited. However, in someembodiments, one or both of the coupling elements 104 and 122 may bepositioned on their respective backplanes such that they may mate withmating portion 154A of the rigid connection 150A. Alternatively, thecoupling elements 104 and 122 may be extended such that both matingportions 152A and 154A are used to couple the chassis 100 and 120together. In further embodiments, the rigid connection 150A may besymmetric, and may be usable for two or more different types of chassis,e.g., a first type of chassis which mates with mating portion 152A (dueto the location of the coupling elements on the chassis) or a secondtype of chassis that mates with mating portion 154A. As indicated above,the circuit board may have circuit portions for performing variousfunctions on the signals being passed between the chassis 100 and thechassis 120. However, in alternate embodiments, the rigid connection150A may simply provide a straight path between the chassis 100 and thechassis 120, e.g., on the mating portion 152A and/or 154A.

Note however, that other styles of mating portions and coupling elementsare envisioned. For example, while in the embodiment shown in FIGS.2A-2C the coupling elements (102, 104, 122, 124) may be half-connectors(e.g., which may be neither male nor female) and the rigid connection(150A) may have edge traces (152A, 154A) which couple to thehalf-connectors, other configurations and types of connectors areenvisioned. For example, in the embodiment shown in FIG. 2D, thecoupling elements (102, 104, 122, 124) may be “female” coupling elementsand the rigid connection 150B may have “male” coupling portions (152Band 154B), or these may be reversed or rearranged in any desirableconfiguration. As another example, the coupling element 104 could bemale, the mating portion 152B could be female, the mating portion 154Bcould be male, and the coupling element 122 could be female, in onepossible configuration.

In one embodiment, instead of a separate rigid connection, each couplingelement may be half of the connection (e.g., where coupling element 104may be male and coupling element 122 may be female). Thus, in thisembodiment, the two coupling elements may form a rigid connection(without requiring the rigid connections 150A or 150B). In otherembodiments, the rigid connection may be any type of connection that issubstantially inflexible and capable of connecting the two chassis,e.g., in an electrical manner. For example, the rigid connection mayinclude hard plastic materials as well as electrical connections.

FIG. 2B illustrates the chassis 100 and the chassis 120 while beingconnected using the rigid connection 150A. More specifically, as shown,the rigid connection 150A is being inserted between the chassis (fromthe front 108, 128) to mate with the coupling elements 104 and 122 (notshown). FIG. 2C shows the chassis 100 and the chassis 120 coupled viathe rigid connection 150A after the insertion of FIG. 2B. Note thatwhile the chassis 100 and the chassis 120 are shown as being similar oridentical, they may still be able to couple when different. For example,in one embodiment, the chassis 100 may be a 4 slot chassis and thechassis 120 may be an 8 slot chassis. Thus, combining the two chassismay effectively create a 12 slot chassis.

FIG. 3—Plurality of Connected Chassis in a Larger Housing

FIG. 3 illustrates a large housing 300 which includes a plurality ofconnected chassis (e.g., as connected in the embodiments of FIGS. 2A and2B). More specifically, the larger housing 300 includes chassis 100,chassis 120, chassis 140, and chassis 160. In this illustration, thefronts of the chassis (100, 120, 140, 160) are shown, and the backplanesfor these chassis are hidden from view inside the large housing 300.

As shown, the larger housing 300 may include an available portion for afifth chassis, as desired. However, the larger housing, or coupling thechassis in general, may not be limited to 4 or 5 connections, but may beextendable to, for example, 8 chassis or, in some embodiments, anynumber of chassis.

In an alternate embodiment, the large housing 300 may itself be achassis, e.g. a PXI chassis or PXI express chassis. In this embodiment,chassis 100, 120, 140, and 160 may be sub-chassis of the chassis 300. Insome embodiments, each of these sub-chassis may connect to a backplaneof the chassis 300 (e.g., via communication interface 106). Thus, thechassis 300 may have a backplane (e.g., for PXI, PXI express, USB, orother bus signals). Additionally, as indicated above, each sub-chassismay include backplanes themselves (e.g., for analog bus signals such astesting signals), which may be connected as disclosed herein. Thus, thebackplanes of the sub-chassis (100, 120, 140, 160) may be coupled asdescribed herein while they themselves are connected a backplane of thechassis 300. However, in alternate embodiments, the sub-chassis bussesmay be any of a variety of busses and the large housing 300 may not haveits own backplane.

Note that in some embodiments the coupled chassis or sub-chassis may beconnected directly to a computer system (e.g. computer system 50), asshown in FIG. 1. However in other embodiments the coupled chassis orsub-chassis may not be capable of connecting directly to a computersystem, e.g. may instead connect to the large housing 300. As notedabove, the large housing 300 may itself be a chassis which may beconnected to a computer system (e.g. computer system 50). Thus, thecoupled chassis or sub-chassis may be able to connect to a computersystem through the large housing 300.

FIG. 4—Method for Connecting a Plurality of Chassis Using a RigidConnection

FIG. 4 illustrates a method for connecting a plurality of chassis usinga rigid connection. The method shown in FIG. 4 may be used inconjunction with any of the computer systems or devices shown in theabove Figures, among other devices. In various embodiments, some of themethod elements shown may be performed concurrently, in a differentorder than shown, or may be omitted. Additional method elements may alsobe performed as desired. As shown, this method may operate as follows.

In 402, a first coupling element of a first chassis may be mated with afirst rigid connection. Similar to depictions above of the chassis 100,the first coupling element (e.g., coupling element 104) may bepositioned on an exterior housing of the first chassis and may mate withthe first rigid connection (e.g., rigid connections 150A or 150B viamating portions 152A or 152B). As indicated above, the first rigidconnection may be a circuit board (e.g., a printed circuit board) whichmay be usable to electrically couple a backplane of the first chassis toa backplane of another chassis.

In 404, a first coupling element of a second chassis may be mated withthe first rigid connection. Similar to depictions above of the chassis120, the first coupling element of the second chassis (e.g., couplingelement 122) may be positioned on an exterior housing of the secondchassis and may mate with the first rigid connection (e.g., matingportions 152A or 154B of the rigid connections 150A or 150B).

Thus, the first chassis and the second chassis may be rigidly connectedusing the rigid connection. More specifically, in one embodiment, therigid connection may provide electrical connectivity between thebackplane of the first chassis and the backplane of the second chassis.Additionally, as indicated above, the rigid connection may includecircuitry or logic which may perform signal processing on signals passedbetween the first and second chassis. In one embodiment, the rigidconnection may provide an access point for backplane signals, e.g., fortesting, possibly using a DMM.

In 406, communication may be performed between the first chassis and thesecond chassis via the rigid connection. In one embodiment,communicating may include transmitting one or more bus signals, e.g.analog bus signals, over the rigid connection. Thus, for example, bussignals may be transmitted from the first chassis backplane to thesecond chassis backplane. However, it should be noted that signals otherthan (or in addition to) bus signals are envisioned. For example, timingsignals, data signals, and/or other types of signals may be transmittedacross the rigid connection (e.g., from the first chassis to the secondchassis, or vice versa).

In 408, a second coupling element of the first chassis may be mated witha second rigid connection. The second coupling element (e.g., couplingelement 102) may be positioned on the exterior housing of the firstchassis. The second rigid connection may be similar to or different fromthe first rigid connection described above, in various embodiments.Additionally, similar to above, the second rigid connection may includelogic or circuitry (and/or embedded passive devices) for performingsignal processing and/or may provide an access point for intercepting orotherwise receiving backplane signals.

In 410, a first coupling element of a third chassis may be mated withthe second rigid connection. Similar to above, the first couplingelement of the third chassis may be positioned on the exterior housingof the third chassis. Thus, the first chassis and the third chassis maybe coupled (e.g., electrically) using the second rigid connection.

In 412, communication may be performed between the first chassis and thethird chassis via the second rigid connection. Similar to above, thecommunication between the first chassis and the third chassis mayinclude bus signals, e.g. analog bus signals, and/or any other types ofsignals, as desired. Note that connecting the third chassis and thefirst chassis may allow communication to occur between the secondchassis and the third chassis (with the first chassis in between). Thus,as one example, signals may be passed from the second chassis to thefirst chassis (via the first rigid connection) and then from the firstchassis to the third chassis (via the second rigid connection).

However, it should be noted that in some embodiments, communicationbetween the first chassis and the second chassis (using the first rigidconnection) may be separate or distinct from communication between thefirst chassis and the third chassis (using the second rigid connection).More specifically, in one embodiment, lines of communication between thefirst and second chassis may be independent from lines of communicationbetween the first and third chassis. However, as already indicated, inalternate embodiments, the lines of communication between the first andsecond chassis and between the first and third chassis may be indistinctor shared.

ADVANTAGES OF THE METHOD

As indicated in the Description of the Related Art, some prior methodsallowed for two chassis to be coupled via cables. However, such cablescan require considerable time and effort by a user connecting the twochassis and can result in misconfiguration. Additionally, cables canbecome tangled and messy and cause signal degradation and latencyproblems (e.g., due to the length of cable involved). Using a short,rigid connection, such as in embodiments described above, overcomes allof these problems. More specifically, signal degradation and latencyproblems do not occur significantly when using appropriate rigidconnections, such as circuit boards. Additionally, connecting aplurality of chassis may allow for an arbitrarily long backplane, e.g.,allowing for the creation of much larger matrices and multiplexers.Thus, the coupling elements and rigid connection allows bus signals(e.g. analog bus signals) (and/or other signals) to propagate seamlesslyto adjacent chassis without the need for cabling. In some embodiments,the rigid connection may provide increased bandwidth when compared totypical wiring solutions.

Additionally, by coupling chassis using a rigid connection, effectivelylarger chassis can be created without introducing separate design cyclesfor such larger chassis. For example, combining three different 4 slotchassis to effectively create a 12 slot chassis does not require amanufacturing company to design and produce a unique 12 slot chassis.

Furthermore, the rigid connections between the different chassis mayprovide a unique ability to test and debug systems. For example, therigid connection may provide a visible connection which provides directaccess to signals between chassis, thereby providing for the ability tomeasure or determine signal characteristics (e.g., directionality),e.g., using a DMM or other signal analyzer. In one embodiment, insteadof a rigid connection connecting two chassis, it is possible to usemeasurement circuitry to test or measure backplane signals sent on thebackplane of a chassis. For example, a measurement PCB could be matedwith a coupling element of a first chassis in order to test or measurebackplane signals of the first chassis. Thus, the measurement PCB couldinclude circuitry for performing testing or measurement of thesebackplane signals.

In some embodiments, the rigid connection may also be able to indicatesignal presence (e.g., with an LED or other indicator), e.g., fordebugging purposes. Additionally, using multiple individual busseswithin a single overall platform such as PXI provides a heretounavailable means to help debug large switching systems.

Although the embodiments above have been described in considerabledetail, numerous variations and modifications will become apparent tothose skilled in the art once the above disclosure is fully appreciated.It is intended that the following claims be interpreted to embrace allsuch variations and modifications.

1. A first chassis, comprising: a housing defining one or more slots andcomprising an exterior; a first backplane comprised in the housing,wherein the first backplane is configured to receive one or more cardsin the one or more slots; and a first coupling element comprised on theexterior of the housing and electrically coupled to the first backplane,wherein the first coupling element is configured to mate with a firstrigid connection in order to convey analog communication through thefirst rigid connection between the first backplane of the first chassisand a second backplane of a second chassis, and wherein a secondcoupling element of the second chassis also mates with the first rigidconnection.
 2. The chassis of claim 1, wherein the first backplaneprovides an analog bus, wherein the one or more slots provide analog busconnections to cards in the one or more slots; wherein the first rigidconnection is configured to convey analog bus signals between the firstand second backplanes.
 3. The chassis of claim 1, wherein the firstrigid connection is configured for use in measuring characteristics ofanalog signals communicated between the first and second backplane. 4.The chassis of claim 1, wherein the rigid connection comprises logicconfigured to perform one or more signal processing functions on analogsignals conveyed between the first backplane of the first chassis andthe second backplane of the second chassis.
 5. The chassis of claim 1,wherein the analog communication includes test and/or measurementsignals.
 6. The chassis of claim 1, wherein the analog communicationincludes timing signals.
 7. The chassis of claim 1, further comprising:a third coupling element comprised on the exterior of the housing andelectrically coupled to the first backplane, wherein the third couplingelement is configured to mate with a second rigid connection in order toconvey analog communication through the second rigid connection betweenthe first backplane of the first chassis and a third backplane of athird chassis, and wherein a fourth coupling element of the thirdchassis also mates with the second rigid connection.
 8. A rigidconnection for coupling two chassis, wherein the rigid connection isconfigured to: mate with a first coupling element of a first chassis,wherein the first coupling element is coupled to a first backplane ofthe first chassis; and mate with a second coupling element of a secondchassis, wherein the second coupling element is coupled to a secondbackplane of the second chassis; wherein after connection, the rigidconnection is configured to convey analog signals between the firstbackplane of the first chassis and the second backplane of the secondchassis, and wherein the first chassis and the second chassis arephysically distinct chassis.
 9. The rigid connection of claim 8, whereinthe rigid connection is configured to provide access to analog signalscommunicated between the first and second backplane, wherein providingaccess to the analog signals communicated between the first and secondbackplane allows characteristics of the analog signals communicatedbetween the first and second backplane to be measured.
 10. The rigidconnection of claim 8, wherein the first and second backplanes eachprovide a respective analog bus, wherein after connection, the first andsecond backplanes effectively provide a combined analog bus.
 11. Therigid connection of claim 8, wherein the rigid connection furthercomprises: logic, wherein the logic is configured to perform one or moresignal processing functions on the analog signals conveyed between thefirst backplane of the first chassis and the second backplane of thesecond chassis.
 12. The rigid connection of claim 8, wherein the rigidconnection further comprises a visible indicator of signal presence. 13.The rigid connection of claim 8, wherein the rigid connection comprisesa printed circuit board.
 14. The rigid connection of claim 13, whereinthe rigid connection is configured to mate with the first couplingelement of the first chassis and the second coupling element of thesecond chassis such that a distance between the first coupling elementof the first chassis and the second coupling element of the secondchassis approximates a thickness of the printed circuit board.
 15. Amethod for coupling a plurality of chassis, comprising: mating a firstcoupling element of a first chassis with a first rigid connection,wherein the first coupling element is positioned on an exterior housingof the first chassis, wherein the first coupling element is coupled to afirst backplane of the first chassis; mating a second coupling elementof a second chassis with the first rigid connection, wherein the secondcoupling element is positioned on an exterior housing of the secondchassis, wherein the second coupling element is coupled to a secondbackplane of the second chassis; wherein the first and second backplanesare each configured to provide a respective analog bus; the firstbackplane communicating analog signals to the second backplane via thefirst rigid connection.
 16. The method of claim 15, wherein, aftermating with the first coupling element of the first chassis and thesecond coupling element of the second chassis, the first rigidconnection provides access to analog backplane signals between the firstand second backplanes, wherein the method further comprises: measuringcharacteristics of the analog signals communicated between the first andsecond backplanes via the rigid connection.
 17. The method of claim 15,wherein said mating the first coupling element of the first chassis andthe second coupling element of the second chassis with the rigidconnection is performed such that, after mating, a distance between thefirst coupling element of the first chassis and the second couplingelement of the second chassis approximates a thickness of the firstrigid connection.
 18. A system, comprising: a housing, wherein thehousing provides a first bus; first and second chassis, wherein thefirst and second chassis are housed in the housing, wherein at least oneof the first and second chassis is coupled to the first bus; wherein thefirst and second chassis respectively comprise first and secondbackplanes each configured to receive one or more cards in one or moreslots of the respective first and second backplanes, wherein the firstand second backplanes each provide an analog bus for the one or morecards received in the one or more slots of the respective first andsecond backplanes; a first rigid connection, wherein the first rigidconnection is coupled to the first and second backplanes in order toconvey analog communication through the first rigid connection betweenfirst and second backplanes.
 19. The system of claim 18, wherein thefirst bus is a different type of bus than the analog busses provided bythe first and second backplanes.
 20. The system of claim 18, furthercomprising: a third chassis, wherein the third chassis is housed in thehousing; wherein the third chassis comprises a third backplaneconfigured to receive one or more cards in one or more slots of thethird backplane, wherein the third backplane provides an analog bus forthe one or more cards received in the one or more slots of the thirdbackplane; a second rigid connection, wherein the second rigidconnection is coupled to the second and third backplanes in order toconvey analog communication through the second rigid connection betweensecond and third backplanes.